1. Field of the Invention
The present invention relates to a method and an apparatus for automatically transporting an article, such as a wafer for producing a semiconductor device, in a vacuum chamber for vacuum treatment of the article. "Vacuum" herein means a rarified atmospheric condition such as that in a chamber below atmospheric pressure, such state being obtained by exhausting the chamber using an air pump.
A semiconductor chip of an integrated circuit device is produced by a process in which a semiconductor wafer is chemically or physically treated in vacuum. For example, a process for coating a film on the wafer or etching the wafer is carried out in a vacuum chamber of a vacuum treatment apparatus, such as a chemical vapor deposition (CVD) apparatus, a dry-etching apparatus, an evaporation apparatus, or a sputtering apparatus. An ion injection method or an electron beam irradiation method for producing a semiconductor chip also carried out in a vacuum.
Today, rapid technical developments in the field of semiconductor devices require automatic treatment of a wafer in order to upgrade the reliability of semiconductor devices and in order to decrease the number of processes for producing the devices, since a large number of fine chips are produced from a wafer. Therefore, the operation of handling the wafer, such as inserting the wafer into the apparatus or removing the wafer from the apparatus, as well as the time and temperature of treatment of the wafer, is controlled by a computer.
The most troublesome part of controlling a vacuum treatment apparatus by computer is the transportation of the water in the vacuum.
2. Description of the Prior Art
Conventionally, a wafer is transported by a mechanical device, such as a claw or a conveyor belt. Such a mechanical device requires lubrication. However, a lubricant cannot be used in the vacuum chamber since it boils off and affects the water in the vacuum. Also, the wafer is treated at a high temperature and corrosive gases are used during the treatment of the wafer, which high temperature and gases affect the claw or conveyor belt. Therefore, the conventional mechanical device for transporting a wafer is not reliable and the parts of the transportation device must often be repaired or replaced.